Flexible DNA target site recognition by divergent homing endonuclease isoschizomers I-CreI and I-MsoI
Flexible DNA target site recognition by divergent homing endonuclease isoschizomers I-CreI and I-MsoI
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DOI：
10.1016/s0022-2836(03)00447-9
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发表时间：
2003-05-30
影响因子：
5.6
通讯作者：
Stoddard, BL
中科院分区：
文献类型：
--
作者：
Chevalier, B;Turmel, M;Stoddard, BL
归巢内切酶是DNA链断裂的高度特异性催化剂，它诱导含有内切酶开放阅读框的移动干预序列的转位。这些酶识别长DNA靶标，同时容忍这些位点内的单个序列多态性。在发现内含子入侵事件后，归巢内切酶本身的序列在很大程度上多样化，产生高度分化的酶来识别相似的靶序列。在这里，我们可视化的机制，灵活的DNA识别和结构分化的模式显示了两个归巢内切酶同分异构体。我们确定了与22个碱基对中8个不同的两个DNA靶点结合的I- crei的结构，以及与几乎相同的DNA靶点结合的同分异构体I- mso I的结构。本研究阐明了DNA结合蛋白混杂碱基对识别的几个原则，并证明了同分异构体显示出明显不同的蛋白质/DNA接触。这些结构使我们能够确定结合位点中单个位置的信息含量，作为直接和水介导的核苷酸碱基接触分布的函数。提供内切酶在其靶特异性分化的早期阶段的进化快照。2003爱思唯尔科学有限公司版权所有。
Homing endonucleases are highly specific catalysts of DNA strand breaks that induce the transposition of mobile intervening sequences containing the endonuclease open reading frame. These enzymes recognize long DNA targets while tolerating individual sequence polymorphisms within those sites. Sequences of the homing endonucleases themselves diversify to a great extent after founding intron invasion events, generating highly divergent enzymes that recognize similar target sequences. Here, we visualize the mechanism of flexible DNA recognition and the pattern of structural divergence displayed by two homing endonuclease isoschizomers. We determined structures of I-CreI bound to two DNA target sites that differ at eight of 22 base-pairs, and the structure of an isoschizomer, I-Mso I, bound to a nearly identical DNA target site. This study illustrates several principles governing promiscuous base-pair recognition by DNA-binding proteins, and demonstrates that the isoschizomers display strikingly different protein/DNA contacts. The structures allow us to determine the information content at individual positions in the binding site as a function of the distribution of direct and water-mediated contacts to nucleotide bases, and. provide an evolutionary snapshot of endonucleases at an early stage of divergence in their target specificity. (C) 2003 Elsevier Science Ltd. All rights reserved.